A typical example of such a medical device is a respirator (also known as a ventilator), at the breathing gas connection of which a tube can be connected via a socket, which said tube leads into the respiration circuit. At their ends facing the respirator, such tubes are provided with transponders, which make it possible for the respirator with an associated writing and reading device to exchange information with the transponder and to make available as a result information on the type and other properties of the connected tube. The antenna of the writing and reading device is located close to the breathing gas connection of the respirator; the antenna can surround this breathing gas connection, for example, concentrically.
One problem of such devices is that a certain distance between the antenna at the fluid port and the transponder at the tube is inevitable, because the socket is located between the tube and the fluid port. Since the range of radio frequency signals, which are exchanged between the antenna of the writing and reading device and that of the transponder, is limited, problems may arise in signal transmission. Another problem is that the connections of the socket to the fluid port, on the one hand, and to the tube, on the other hand, do not predetermine a fixed or predetermined rotation position of the fluid port and the socket, on the one hand, and the socket and the tube, on the other hand, i.e., the connections may take place, in principle, in any relative rotation position of the components in relation to one another, i.e., both the rotation position of the socket in relation to the fluid port and the relative rotation position of the socket in relation to the tube may vary over a relative angle of rotation of 360°. The position which the antenna of the transponder will assume relative to the antenna of the writing and reading device is unpredictable due to these circumstances.
Furthermore, the rotatable connection of the fluid port or the tube to the socket rules out an electrically conductive connection from practical points of view, because such a connection could be embodied only at a considerable design effort, for example, with sliding contacts.